#include<bits/stdc++.h>

#define ll long long
#define pi pair<ll,ll>
#define vi vector<ll>
#define cpy(x,y,s) memcpy(x,y,sizeof(x[0])*(s))
#define mset(x,v,s) memset(x,v,sizeof(x[0])*(s))
#define all(x) begin(x),end(x)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define ary array
#define IL inline

#define mod 998244353
#define N 200005

using namespace std;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0' || ch>'9')f=(ch=='-'?-1:f),ch=getchar();
    while(ch>='0' && ch<='9')x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
    return x*f;
}
void write(ll x){
    if(x<0)x=-x,putchar('-');
    if(x/10)write(x/10);
    putchar(x%10+'0');
}

ll a[N],b[N];

void solve(){
	ll m=read(),suma=0,sumb=0;a[m]=b[m]=0;
	for(ll i=0;i<m;i++)a[i]=read(),suma+=a[i];
	for(ll i=0;i<m;i++)b[i]=read(),sumb+=b[i];
	ll pos=m-1,res=0,flag=0;
	if(suma<sumb)a[0]+=sumb-suma;
	else b[0]+=suma-sumb;
	
	ll lasA=0,lasB=0;
	for(ll i=0;i<m;i++)lasA=(a[i]?i:lasA),lasB=(b[i]?i:lasB);
	
	for(ll i=0;i<m;i++){
		while(pos!=-1 && a[i] && pos+i>=m-1){
			if(!b[pos]){pos--;continue;}
			ll d=min(a[i],b[pos]);
			b[pos]-=d;a[i]-=d;flag|=(pos+i>=m);
			res+=d;
			if(!b[pos])pos--;
		}
	}
	for(int i=0;i<=lasA;i++)if(b[m-i])flag=1;
	for(int i=0;i<=lasB;i++)if(a[m-i])flag=1;
	
	if(res && !flag)res--;
	write(res);putchar('\n');
}

int main(){
	#ifdef EAST_CLOUD
	freopen("a.in","r",stdin);
	#endif
	ll T=read();while(T--)solve(); 
	
}
//cerr<<fabs(&Med-&Mbe)/1048576.0<<"MB\n";
//cerr<<"\n"<<clock()*1.0/CLOCKS_PER_SEC*1000<<"ms\n";